3.5". While extremely clean the button does have denting obvious on the reverse but not so much on the front. Metal back has three small dents on the outer edge where it raises up to hold the celluloid front. Center area also has .5" dent line along the left. Front of the piece displays cleanly although small dented area on the bottom going upward about an 1" and going over about 1.5". There is also a pair of faint hairline scratches beneath the date but they really only show in reflected light and the piece still has full gloss and no stain. Only about the third we've been able to offer in five decades.